In the Diabetes Surgery Study, the American Diabetes Association composite endpoint -- HbA1c <7.0%, LDL cholesterol <100 mg/dL, and systolic blood pressure <130 mm Hg -- was achieved by 23% at 5 years post-gastric bypass versus only 4% with non-surgical management (P=0.01), according to Charles Billington, MD, of the University of Minnesota in Minneapolis, and colleagues.

"In the 5-year follow-up, adding gastric bypass to intense lifestyle and medical management continued to show improved attainment of the triple diabetes endpoint goal. However, the 5-year results for gastric bypass of 23% and lifestyle plus intense medical management of 4% maintaining the endpoint goal were significantly lower than the first-year rates of 50% and 16%," the authors reported online in the Journal of the American Medical Association. The gap in the composite endpoint had narrowed in the third year and remained stable thereafter.

The report was one of several bariatric surgery studies published in the journal as part of a package on obesity. MedPage Today has further coverage here and here.

The Diabetes Surgery Study "is now the third randomized controlled trial with 5-year follow-up comparing surgical treatment with medical treatment for type 2 diabetes that shows surgical treatment, gastric bypass, to be superior to medical management in achieving optimal glycemic control. All three studies are remarkably consistent with respect to achieving the primary endpoint in favor of surgery as well as demonstrating durability out to 5 years," commented Philip Schauer, MD, of the Cleveland Clinic.

He told MedPage Today that the study "is unique in demonstrating not just superior glycemic control for surgically treated patients, but also superior outcomes for surgery in terms of the composite endpoint of blood sugar, blood pressure, and lipids."

"These results further strengthen the rationale for surgery to treat type 2 diabetes, especially in patients not well controlled with medication, as noted in the 2018 American Diabetes Association Guidelines for treatment of diabetes as well as international guidelines," said Schauer, who was not involved in the study.

The study randomized participants to a lifestyle-intensive medical management intervention for 2 years with or without Roux-en-Y gastric bypass. Participants, recruited from four sites in the U.S. and Taiwan, were obese patients with BMI in the 30.0-39.9 range. Similar baseline characteristics existed between groups.

"Because most participants had good baseline control of blood pressure and LDL-C and because the treatment effect on these variables was weaker, glycemic control is likely the primary contributor to the surgical composite triple endpoint improvement," the authors suggested.

By year 5, 55% of the surgery group versus 14% of the controls had achieved HbA1c <7.0% (P=0.002). "These achievement rates are higher than for the primary composite triple endpoint but were also significantly reduced from the corresponding 1-year values of 83% in the surgical group and 29% in the lifestyle/medical management group," the investigators noted.

As expected, patients randomized to surgery had more serious adverse events (66 versus 38 events), most frequently GI events and surgical complications such as strictures, small bowel obstructions, and leaks.

"The mean baseline HbA1c concentration of 9.6% indicates that this was a group of participants with relatively poorly controlled glycemia, so whether the results would be different with better controlled glycemia at baseline cannot be determined," Billington's group acknowledged. "Similarly, the participants had diabetes for a mean of 9 years at study entry, so treatment effect on diabetes of lesser duration could be different."

Moreover, the Diabetes Surgery Study is limited by its unknown applicability to bariatric surgical approaches other than gastric bypass.

Billington disclosed support from Medtronic, the NIH, and the Department of Veterans Affairs, and relevant relationships with Novo Nordisk, Enteromedics, and Optum.

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